Vocore + RTLSDR

Posts: 1
Joined: Wed Jan 18, 2017 5:27 am

Vocore + RTLSDR

Wed Jan 18, 2017 6:37 am

Hello there!

After my Vocore started collecting dust in my cupboard, I finally decided to mess around with it again.
So I've set up a Linux VM to compile the new firmware (My vocore was still running Barrier breaker..) and I've noticed that OpenWrt has a package called "RTLSDR".

Short info about RTLSDR: These are utilities to turn a rtl2832u-based DVB-T dongle into a software defined radio with a frequency range from ~25 MHz to 1.7 GHz, depending on the tuner.

I thought: Hell no, this won't work with this thing, because the Vocore has way lower specs than a raspberry pi and I don't have audio.. Meeh, let's give it a try.

So I've compiled it in and soldered a USB Port on the Vocore, installed the firmware and checked if the dongle is recognised properly. It worked!
Because my Vocore does not have audio output (No dock..) I gave it a try with rtl_tcp. I fired SDRsharp up on my computer, configured it to use rtl_tcp, 1.024 MSps and it just worked. I was able to listen to FM radio, pager signals and so on.. Although tuning to frequencies was a bit slow.
While playing around I also noticed that my Vocore was getting REALLY hot, so I've salvaged a little heat spreader from a spare router. Still the Vocore reaches 70°C.
After confirming everything works I've decided to directly solder the Vocore to the RTLSDR dongle and put rtl_tcp into the /etc/rc.local so it starts on boot.

I plugged my "Vocore-Dongle" into a USB charger and I was surprised that suddently the RTLSDR Dongle was not being recognised.
Problem was: Some chargers probably short the USB data pins or use resistors- that causes the the Vocore to stop recognising the dongle. After cutting the data wires on a short USB extension lead it worked again.

So what is the point of doing this whole thing?
Yes, I could've just plugged the RTLSDR Dongle into my PC directly, but I have problems with RFI from my power supplies and my flatscreen. By using the VoCore as a rtl_tcp server I am able to move the dongle far away from my noisy equipment.

The setup still has some bugs: sometimes the rtl_tcp server does not start correctly on boot (Probably a network issue. I need a proper init.d script...) and needs to be restarted. Sometimes (when tuning around too fast) the Vocore completely freezes and needs a restart.
VoCore 3.jpg
Small hole in the actual RTLSDR dongle. The wires directly go to the USB dongle. A power supply powers both the dongle and the VoCore
VoCore 3.jpg (156.82 KiB) Viewed 697 times
VoCore 2.jpg
VoCore 2.jpg (195.71 KiB) Viewed 697 times
VoCore 1.jpg
The assembled dongle with antenna. The three random wires are the serial console
VoCore 1.jpg (236.74 KiB) Viewed 697 times

Posts: 553
Joined: Sun Oct 19, 2014 6:00 am

Re: Vocore + RTLSDR

Thu Jan 19, 2017 11:41 am

Haha, not sure what it is, but looks awesome. :)

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